Adsorption and redox reactions of heavy metals on synthesized Mn oxide minerals

Feng, Xiong Han; Zhai, Li; Tan, Wei; Fan, Louzhen; He, Ji Zheng

doi:10.1016/j.envpol.2006.05.028

Cited by 270 publications

(152 citation statements)

References 32 publications

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“…Ga, Gd, Hg, In, Ru, and Sc) plus Al and La (Kopittke et al 2008) have an ionic index >8 (Nieboer and Richardson 1980). We propose that the binding of metals increases cell wall rigidity through covalent bonding (specific adsorption) also; lower pK a values favouring specific adsorption for cations (McKenzie 1980;Feng et al 2007). Of the nine monovalent or divalent cations examined, Hg and Cu had the lowest pK a values, and hence would be expected to bind the strongest to pectin in the cell wall (pK a values: Hg=3.4, Cu=7.6, Pb=7.7, Zn=9.0, Co=9.6, Ni=9.9, Cd=10.1, Ca=12.8, Tl=13.2;Baes and Mesmer 1986;Wulfsberg 2000).…”

Section: Discussionmentioning

confidence: 94%

Metal-induced cell rupture in elongating roots is associated with metal ion binding strengths

et al. 2009

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Low concentrations of Al, Cu and La rapidly decrease root elongation and cause transverse ruptures to the rhizodermis and outer cortex, but it is not known if other trace metals have similar effects. Six trace metals, Ga, Gd, Hg, In, Ru, and Sc, decreased cowpea root growth and caused ruptures similar to those caused by Al, Cu and La. Calculated speciation of the metals showed that only Gd was almost exclusively present as the trivalent ion (Gd 3+ ), but the other test solutions were dominated by Ga (OH) 2 + , HgCl 2 0 , either In 3+ , In(OH) 2+ , In(OH) 2 + , In (OH) 3 0 , or InCl 2+ , and Sc 3+ or ScOH 2+ (no thermodynamic constants were available for Ru). The results from this and other studies suggest that the ability of these trace metals (plus Al, Cu, and La) to cause ruptures is related to the strength to which the trace metals bind to the cell wall. Therefore, it is proposed that the toxic effects of trace metals results from (1) the strength of binding (either ionically or covalently), and (2) other toxic effects of the metals not dependent on cell wall interactions.

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Section: Discussionmentioning

confidence: 94%

Metal-induced cell rupture in elongating roots is associated with metal ion binding strengths

et al. 2009

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“…Studies have indicated that birnessite structural vacancies account for the negative layer charges and are associated with adsorption of Pb, Zn, Cu, Cd, and Ni, oxidation of Co 2+ and Cr 3+ , and conversion of birnessite (Appelo and Postma 1999;Burns 1976;Lanson et al 2002a;Manceau and Charlet 1992;Manceau et al 2002;Peacock and Sherman 2007;Toner et al 2006). Feng et al (2007) found that the adsorption affinity and capacity of birnessites differed for different heavy metal ions. Among heavy metal ions, birnessites possess the greatest adsorption affinity and capacity for Pb 2+ .…”

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confidence: 97%

Pb2+ adsorption on birnessite affected by Zn2+ and Mn2+ pretreatments

et al. 2010

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Purpose Lead contamination is ubiquitous, and much attention has been paid due to its toxicity. The phyllomanganate birnessite is the most common Mn oxide in soils. The MnO 6 octahedral layers may have significant Mn vacancies in the hexagonal birnessites. Among heavy metal ions, birnessites possess the greatest adsorption affinity and capacity for Pb 2+ . The aim of this study was to understand the relationship between vacant Mn octahedral sites and Pb 2+ adsorption. Materials and methods Birnessite synthesis was achieved by the reduction of potassium permanganate in a strong acidic medium. Synthetic birnessite was then treated with Mn 2+ or Zn 2+ at different concentrations. Isothermal Pb 2+ adsorption on birnessite before and after treatments was measured at a solid-to-liquid ratio of approximately 1.67 g/L, and Pb 2+ concentrations ranged from 0 to 10 mmol/L with an ionic strength of 0.1 mol/L NaNO 3 . The amount of Pb 2+ adsorbed and the amount of Mn 2+ or Zn 2+ released during the whole adsorption process were obtained by comparison with a control group without adding Pb 2+ . The amount of H + released was determined from the recorded additions of standard HNO 3 /NaOH solutions. Results and discussion Mn average oxidation state (AOS) and d(110)-interplanar spacings of the birnessites remained almost unchanged as the concentration of the treating Zn 2+ increased, indicating an unchanged number of vacant Mn octahedral sites, whereas the maximum Pb 2+ adsorption decreased from 3,190 to 2,030 mmol/kg due to the presence of Zn 2+ on adsorption sites. The AOS's of the Mn 2+ -treated birnessites decreased and most of the Mn 2+ ions added were oxidized to Mn 3+ ions. The d(110)-interplanar spacing of Mn 2+ -treated birnessites increased from 0.14160 to 0.14196 nm, indicative of a decreased vacant Mn octahedral sites. Moreover, the maximum Pb 2+ adsorption of Mn 2+ -treated birnessites decreased from 3,190 to 1,332 mmol/kg, the decrease being greater than that for the corresponding Zn 2+ -treated birnessites. Conclusions Most Mn 2+ was oxidized to Mn 3+ by birnessite, with a portion of Mn 3+ located above or below vacant sites, which did not affect the number of vacant sites, and the remaining Mn 3+ migrating to occupy the vacant sites. In contrast, Zn 2+ ions are adsorbed only above or below vacant sites. Birnessite Pb 2+ adsorption capacity is determined largely by the number of vacant Mn sites.

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“…Fe-doped cryptomelanes were prepared by adding KMnO 4 solution to mixtures of Fe 2 (SO 4 ) 3 , MnSO 4 and acetic acid at different molar ratios of Fe/Mn using the reflux method under atmospheric pressure [12]. In a typical procedure, 80 mL of 0.4375 mol/L KMnO 4 solution was heated to 60°C and poured into 100 mL mixtures of Fe 2 (SO 4 ) 3 and MnSO 4 solutions (the molar ratio of Fe/Mn is 0, 0.03, 0.08 or 0.10).…”

Section: Preparation Of Fe-doped Cryptomelane Samplesmentioning

confidence: 99%